1. Field of the Invention
The present invention relates to a method of manufacturing a semiconductor device and a support structure for a semiconductor substrate used for the method.
2. Description of the Related Art
With growing demands for smaller and higher performance semiconductor devices in recent years, packaging of semiconductors is required to have smaller size and provide for higher performance.
For example, there has been a demand for reducing thickness of semiconductor devices. To meet this demand, it is necessary to reduce the thickness of packaged semiconductor substrates by increasing a grinding amount in a so-called backgrinding process, where a back face of a semiconductor substrate or a face opposite to a face on which semiconductor device elements are formed is ground to reduce the thickness of the semiconductor substrate.
FIG. 1 is a schematic illustration of a semiconductor device 10 having a CSP (Chip Size Package) structure, which is an example of a structure that allows size reduction of semiconductor devices.
Referring to FIG. 1, the semiconductor device 10 comprises a semiconductor substrate 11, which may be a Si wafer or the like, having a device face 11A on which semiconductor device elements are formed and a back face 11B opposite to the device face 11A. Plural electrode pads 12 made of Al or the like are formed on the device face 11A. A passivation layer 12A made of SiN or the like is formed to cover the device face 11A except where the electrode pads 12 are formed. The passivation layer 12A is covered by a passivation layer 13 made of resin such as polyimide. Further, the passivation layer 13 is covered by a sealing resin layer 15.
Wiring sections 14 made of Cu are formed in openings in the passivation layer 12A and the passivation layer 13 to be connected to the electrode pads 12. The wiring sections 14 are patterned to extend partly onto the passivation layer 13.
Wiring posts 16 are formed upright on the wiring sections 14 formed on the passivation layer 13 to be connected to the wiring sections 14. A side surface of each of the wiring posts 16 is surrounded by the sealing resin layer 15, but an upper end thereof is exposed from the sealing resin layer 15. A barrier metal layer 17 is formed on the exposed upper end of each of the wiring posts 16. A bump ball 18 made of solder or the like is formed on the barrier metal layer 17.
In this type of semiconductor device having a CSP structure, wiring connecting semiconductor device elements to metal bumps is highly densely formed on a semiconductor substrate. Therefore, it is possible to reduce the size of the semiconductor device.
For further reduction of size or thickness of the semiconductor device, a thickness D of the semiconductor substrate needs to be reduced. Therefore, attempts to make the semiconductor device thinner by grinding the back face 11B have been made in semiconductor device packaging techniques.
However, thickness reduction of semiconductor substrates increases defects such as damage to or warpage of semiconductor substrates, and therefore lowers production yield of semiconductor devices. There have been some attempts to prevent defects due to thickness reduction of semiconductor substrates by forming a passivation film on a back face of a semiconductor substrate (see, for example, Japanese Patent Laid-Open Publications No. 2002-231854 and No. 2002-270720).
If, however, a passivation film is formed on a back face of a semiconductor substrate, the semiconductor device becomes thicker. Thus, thickness reduction of semiconductor devices remains difficult.
Another problem with forming a passivation film on a back face of a semiconductor substrate is that the passivation film is often partly separated from the semiconductor substrate in a process of forming a semiconductor device. Especially, a passivation film having properties (e.g. rigidity) different from those of a semiconductor substrate is often separated from the semiconductor substrate in a so-called dicing process where the semiconductor substrate is cut into chips. Such partial separation of the passivation film also lowers production yield of semiconductor devices.